Surgical tourniquet systems are commonly used to stop the flow of arterial blood into a portion of a patient's limb, thus creating a clear, dry surgical field that facilitates the performance of a surgical procedure and improves outcomes. A typical surgical tourniquet system of the prior art includes a tourniquet cuff for encircling a patient's limb at a desired location, a tourniquet instrument, and flexible pneumatic tubing connecting the cuff to the instrument. In some surgical tourniquet systems of the prior art, the tourniquet cuff includes an inflatable portion, and the inflatable portion of the cuff is connected pneumatically through flexible plastic tubing and one or more connectors to a tourniquet instrument.
A typical tourniquet instrument of the prior art includes a pressure regulator to maintain the pressure in the inflatable portion of the cuff, when applied to a patient's limb at a desired location, near a reference pressure level that is above a minimum pressure required to stop arterial blood flow past the cuff during a time period suitably long for the performance of a surgical procedure. The reference pressure level may be set manually by a user, it may be determined automatically for an individual patient, or it may adapt automatically during a surgical procedure. Many types of such pneumatic surgical tourniquet systems have been described in the prior art, such as those described by McEwen in U.S. Pat. No. 4,469,099, No. 4,479,494, No. 5,439,477 and by McEwen et al in U.S. Pat. No. 5,607,447, No. 5,855,589 and No. 7,479,154.
Tourniquet instruments known in the prior art are not fully integrated with the tourniquet cuffs connected to them, or with ancillary apparatus in the operating room. As a result, typical prior-art tourniquet systems cannot change their operation in ways that could significantly improve their safety, performance and reliability.
The earliest surgical tourniquet systems of the prior art were entirely mechanical and thus had no integration or connectivity with other apparatus in the operating room. The invention and introduction into practice of the first surgical tourniquets employing digital technology, as described by McEwen in U.S. Pat. No. 4,469,099, enabled their integration with other apparatus in the surgical suite and with digital operating-room information systems. For example, in U.S. Pat. No. 4,479,494 McEwen describes a tourniquet system communicating with apparatus monitoring the surgical patient's blood pressure, thereby allowing the tourniquet system to receive blood pressure information and adapt tourniquet cuff pressure accordingly, and communicating with a separate printer to remotely record and display information relating to tourniquet operation. Ulrich in U.S. Pat. No. 5,569,304 describes tourniquet apparatus communicating with automatic blood pressure measuring apparatus. As another example, in U.S. Pat. No. 5,607,447 McEwen and Jameson describe a tourniquet system having an internal event register for storing certain predetermined events relating to tourniquet usage, and including connectivity allowing the recording and display of the stored events by a remote printer.
Typically, surgical tourniquet systems of the prior art have included means for enabling tourniquet cuff pressure to be set to levels of pressure that do not exceed a maximum limit. The earliest prior-art tourniquet systems often had maximum limits determined by the apparatus itself, for example by the maximum limit of the specific pressure regulator employed or by the maximum pressure of the source of gas supplying the pressure regulator. In one such system known in the prior art, the maximum limit that could be set by a user was 1000 mmHg.
Evidence from many studies published in the medical literature over the years has demonstrated that higher tourniquet pressures are associated with higher probabilities of patient injuries. Following the introduction of digital tourniquet systems such as those described by McEwen in U.S. Pat. No. 4,469,099, their increased accuracy, reliability and safety allowed users to routinely set lower and safer maximum limits in tourniquet systems based on patient safety considerations. For some prior-art surgical tourniquet systems that are widely used at present, the maximum limit is 475 mmHg. The lower maximum limit is intended to help prevent inadvertent or unintentional setting of tourniquet cuff pressure to hazardous levels higher than needed to stop arterial blood flow for the duration of a surgical procedure. A predetermined maximum limit of tourniquet pressure based on patient safety has proven to be satisfactory for almost all normal adult patients undergoing surgery in normal limbs that are encircled by standard tourniquet cuffs.
However, for some surgical patients, limbs and situations, the predetermined maximum limit to which pressure can be set in known prior-art tourniquet systems may be insufficient to stop arterial blood flow and thus establish a bloodless field to facilitate surgery. Examples include: patients who are very obese; patients who have certain abnormal medical conditions such as hypertension; patients who have abnormal physiology or anatomy, including calcified arterial vessels or limbs of large circumference; and situations where certain non-standard types of tourniquet cuffs are used. Alternatively, for some patients and limbs and situations, the predetermined maximum limit of known prior-art tourniquet systems may be much higher than required to stop blood flow, and thus may allow tourniquet pressure to be set to levels that are unnecessarily and hazardously high. For example, lower tourniquet pressure settings are typically sufficient and safer for many pediatric patients, for adult patients who are of small physical size or who have limbs of small circumference, and when tourniquet cuffs having variable-contour shapes and greater widths are employed.
Leakage of pressurized gas from the tourniquet cuff, from pneumatic tubing between the instrument and cuff, and from connectors that attach the tubing to the cuff and instrument may affect tourniquet safety, performance, and reliability. Accordingly, the 2007 Recommended Practices for the Use of the Pneumatic Tourniquet in the Perioperative Practice Setting (RPs) of the US Association of periOperative Nurses (AORN) recommend that the tourniquet cuff, tubing, and connectors should be kept clean and in good working order. The AORN RPs further recommend, based on published literature, that the tourniquet cuff, tubing and connectors should be inspected for cracks and leaks because unintentional pressure loss can result from loose tubing connectors, deteriorated tubing, or cuff bladder leaks, and may result in patient injury. At present, because tourniquet systems of the prior art are not fully integrated with the cuffs connected to them through tubing and connectors, such inspections and checking are performed manually and often inconsistently, or only after a hazardous incident or patient injury has occurred.
To best comply with the 2007 AORN Recommended Practices regarding inspection and checking of tourniquet cuffs, connectors, and tubing, their pneumatic integrity should be routinely checked between surgical procedures and surgical staff should be alerted to any potential hazards found so that remedial action can be taken promptly. If this is not done, then leaking and potentially hazardous tourniquet cuffs, connectors, and tubing may be used for surgery, and may remain in use for long periods of time. Also, users may not be alerted to defects which may be small initially but which may increase to become significant hazards for patients, either slowly or very rapidly. Additionally, unauthorized reprocessing and reuse of cuffs manufactured to be single-use disposable cuffs may introduce leakage hazards if such cuffs are not carefully inspected before each reuse, or after each reuse, because improper, uncontrolled and unlimited reprocessing may impair the shape and integrity of the pneumatic seals of cuff connectors. Even if disposable tourniquet cuffs are used as single-use products, and if it is assumed that such cuffs are not leaking at time of first use, the tubing and connectors that connect the disposable cuffs to the tourniquet instrument may leak and such leakage may go undetected, allowing the leaking tubing or connectors to remain in use until an obvious patient hazard or injury occurs, and during which time other limitations in tourniquet safety, performance and reliability are produced.
Pneumatic leakage in tourniquet systems that is not detected by routine inspections and checking is undesirable in surgery and may be hazardous. In the past, undetected pneumatic leakage led users of prior-art systems to set tourniquet pressures at reference levels that were substantially higher than required physiologically to compensate for intra-operative reductions in cuff pressure that users had observed but had not been able to attribute to obvious leakage. However, setting unnecessarily high pressures is hazardous because in the medical literature higher tourniquet pressure levels have been associated with higher probabilities of patient injuries to nerves and soft tissues. More recently, some surgical tourniquet systems of the prior art have attempted to compensate for undetected levels of pneumatic leakage in the design of their pressure regulators. In typical systems, the pressure regulator is designed to maintain cuff pressure within a predetermined pressure range from a reference pressure, and any fluctuations beyond that range are offset by actuation of a pump, reservoir, or valve in an effort to bring the cuff pressure back within the range. If there is pneumatic leakage sufficient to cause the cuff pressure to decrease beyond the predetermined pressure range, actuation of the pressure regulator may bring it back within range, and if not a pressure-regulation alarm is produced. Such systems of the prior art may compensate for significant levels of sustained, undetected leakage without producing any indication of leakage or alarm for the user. Further, sustained leakage may produce an error in the indicated tourniquet cuff pressure in single-port tourniquet systems of the prior-art which estimate cuff pressure by measuring pneumatic pressure within the tourniquet instrument. For typical surgical tourniquet systems of the prior art, three limitations in the performance and reliability of their pressure regulators exist in the presence of undetected pneumatic leakage. First, tourniquet cuff pressure fluctuates unnecessarily as decreases in cuff pressure are offset by the actuations of the pressure regulator. Second, unnecessarily frequent actuation of the pressure regulator reduces the operational life and reliability of its mechanical components, increases the cost of maintaining and replacing those components, and may increase capital costs by necessitating early replacement of the entire tourniquet instrument. Third, operation of prior-art tourniquet systems on battery power is impaired. Typical tourniquet systems of the prior art may be powered either by external AC power or by an internal battery, so that they can continue to operate safely in the event of a sudden interruption of external power, and so that they can operate independently of external AC power for a prolonged period of time, for example during transportation of a patient from a pre-operative room to the operating room, or to facilitate surgery under emergency or battlefield conditions. However, in the presence of sustained leakage pneumatic leakage, the operational time of a tourniquet system when powered by an internal battery for surgery may be substantially reduced due to unnecessary actuations of the pressure regulator. Additionally, the overall life of the internal battery may be significantly reduced, reducing the performance and reliability of the tourniquet system and thereby increasing costs and hazards.
There is a need for a surgical tourniquet system that overcomes the above-described limitations of the prior art. For example, no system is known in the prior art that prevents the inadvertent or unintentional setting of tourniquet pressure to a level substantially higher than needed for one individual surgical patient, and yet allows such high pressure levels to be set if needed to stop blood flow in another individual patient. As another example, no tourniquet system known in the prior art includes means for automatically checking the integrity of its pneumatic components prior to each use, or after each use, or for identifying, recording and alerting the user to possible hazards identified by such checking. As yet another example, no known prior-art tourniquet system communicates information about the results of such pneumatic integrity checking, or information on individualized maximum pressure limits, to a remote display, printer or other apparatus to inform the user, to record the information for quality assurance, or for other purposes.